in nevada the president who has been rehearsing with massachusetts senator john kerry as romney went to the hoover dam. >> it's spectacular. >> reporter: both left the day's campaigning to their number twos and that turned into trouble for team obama. in charlotte, vice president joe biden was trying to argue romney would raise taxes on the middle class. when he implied president obama's policies already have hurt. >> how they can justify raising taxes on the middle class that's been buried the last four years. how in lord's name can they justify raising their taxes. >> reporter: biden later tried to dig out of that hole but republicans pounced. >> vice president biden just today said that the middle class over the last four years as been quote buried. we agree. we need to stop digging by electing mitt romney as the next president of the united states. >> reporter: the day's events were overshadowed by a video of senator obama reading off a prepared script. before a predominantly black audience he inplayed the federal government held back money after hurricane katrina based on race.